Clinical significance of incidental focal [18F]-FDG uptake in small bowel on PET-CT

Objectives There is little evidence to inform investigative pathways for incidental focal uptake of [18F]-FDG in the small bowel on PET-CT, resulting in uncertainty around optimal management in clinical practice. We aimed to assess the proportion of these patients with clinically significant findings on follow-up investigation. Methods We conducted a retrospective service evaluation of all [18F]-FDG PET CT examinations (n = 25,050) conducted at our tertiary centre and identified 187 patients with unexpected focal small bowel [18F]-FDG uptake, 68 of which subsequently underwent further investigation to characterise the nature of uptake, including CT/MRI enterography, direct visualisation, and repeat PET-CT. We also performed statistical analysis to determine if a SUVMax cutoff could be used to predict the nature of focal uptake (i.e pathological vs non-pathological). Results 14 out of 68 patients had findings which required further medical treatment or monitoring, 8 (57%) of which were malignant. Only 5 of the 14 patients (35%) had an identifiable abnormality on the low-dose CT component, although pathological lesions were revealed in 7 of the remaining 9 patients following dedicated small bowel investigations. We did not find a significant difference in SUVmax between pathological and physiological uptake. Conclusion Based on our series, up to 1 in 5 patients with incidental small bowel uptake without CT abnormalities may have significant findings requiring treatment. Advances in knowledge This study supports the recommendation of dedicated cross sectional small bowel imaging or small bowel endoscopy to investigate incidental small bowel [18F]-FDG uptake, an entity with variable practice in reporting PET-CT.